This section is intended to introduce various aspects of the art, which may be associated with exemplary embodiments of the present invention. This discussion is believed to assist in providing a framework to facilitate a better understanding of particular aspects of the present invention. Accordingly, it should be understood that this section should be read in this light, and not necessarily as admissions of prior art.
Seismic stratigraphy analyzes sediments and sedimentary rocks in a geometrical context derived from seismic reflections. A typical first step is the separation of seismic-sequence units which is usually done by mapping significant surfaces from where they are indicated by terminations of seismic reflections or seismic reflections with different orientation butting into each other. A second step is the characterization of these seismic-sequence units, a process aided by prior determination and classification of the terminations as truncation, toplap, onlap or downlap. Picking and classifying terminations is traditionally a manual task where the interpreter examines the data and marks terminations, for example with a little arrow.
Existing methods for computer-assisted seismic stratigraphy relate to the detection of convergences in seismic images or sections. Representative examples thereof are disclosed by T. Randen et al., “New Seismic Attributes for Automated Stratigraphic Facies Boundary Detection”, SEG Technical Program, Expanded Abstracts, pp. 628-631, 1998 and A. Barnes, “Attributes for Automating Seismic Facies Analysis”, SEG Technical Program, Expanded Abstracts, pp. 553-556, 2000.
Both of these methods share the need for preliminary determination of a “field of directional vectors” at every pixel of the data. In Barnes' work, quantification of the reflectors convergence is obtained by calculating the divergence of the field of directional vectors. In Randen's work, the directional field is subjected to a search for flowlines whose density expresses the divergence or the convergence of the reflectors. Neither method involves a notion of a surface that separates two stratigraphic units formed under different sedimentological conditions.
In Randen's case, terminations can be defined as locations where flowlines intersect or approximately merge. With an appropriately chosen flowline density, the intersections pinpoint the boundaries by virtually continuous lines, provided sufficient quality and clarity of the seismic data. Randen et al., however, discloses neither further details on requirements for data quality and data clarity nor specifics about flowline generation or intersection detection. In Barnes' case, terminations are best defined in terms of termination density without ability for further classification.
Neither case allows for the automatic detection and classification of individual terminations. Thus, there is a need for improvement in this field.